This experiment was designed for the evaluation of the usefulness of enzyme histochemistry in the determination of the lapse of time in brain wound, and also for the establishment of medicolegal 'biological time table' on brain wound. Brain injury was made by contusion and laceration of meninges and brain itself in rats. The results were as follows; 1) By routine histological technique, estimation of the lapse of time in brain wound could be possible 4 hours after the infliction of wound. 2) The earliest change of enzyme activities was recognizable by the decreased activities of ATPase and succinic dehydrogenase 30 minutes after the injury. These decreased enzyme activities were not recovered up to the 4th day after the brain injury. 3) Increased acid phosphatase activity was noticed 1 hour, and beta-glucuronidase, 2 hours after the injury in a mild degree. Both increased activities were pronounced following the lapse of time in brain wound. 4) No significant change was seen in alkaline phosphatase, monoamine oxidase, non-specific esterase and leucine aminopeptidase activities throughout the experimental period up to the 4th day. So the enzyme histochemistry of these enzymes seemed to be little valuable for the study on the timing of wound in brain injury. In the light of these results it appeared that the enzyme histochemistry, in particular of ATPase, succinic dehydrogenase, and acid phosphatase, for the estimation of timing of brain wound not only shortened the histological "lag period" up to 30 minutes after the injury, but also provided a useful information in determining the biological time table following the brain injury.